I Love You Phillip Morris begins by telling us that it's based on a true story. Then, as if we might be disbelieving of that claim, it reinforces it. Truth, as they say, is stranger than fiction. (Not really, but the phrase sounds good, so we use it.) At times, I Love You Phillip Morris verges on genius. On other occasions, it falls into a rut and has trouble getting back on the blacktop. As a comedy, it crackles with deadpan wit and dark satire. As a romance, it lacks vigor. And, on those occasions when it ventures into dramatic territory, it is rarely effective. Ultimately, the plot (irrespective of how faithful it is to real life) isn't the problem - it's the unevenness with which co-directors Glenn Ficarra and John Requa (both making their directorial debuts) approach it that limits the film's success and mutes the experience of sitting through it.

Jim Carrey was born to play Steven Russell, the con man protagonist with the rubber face and the oversized smile. It's as if the role was tailored for him, and he has no trouble with the slightly exaggerated approach demanded by the comedic elements. Ewan McGregor, however, is less impressive. The part of Phillip Morris, a sweet guy with a Southern accent, demands a deft approach that eludes McGregor, who mistakes "one-note" for "low-key." He's too earnest and, as a result of the mismatch in style and energy level, there's too little chemistry for the romance to work as more than a plot necessity. The devaluation of the love story limits the effectiveness of the few genuinely dramatic moments, leaving the comedy as the lone standout aspect of I Love You Phillip Morris.

The movie begins with Steven Russell (Jim Carrey) apparently on his deathbed. His story to that point is related via flashbacks, with Steven providing a tongue-in-cheek voiceover narrative. He spends his early adult life assimilating into suburbia, playing the role of the perfect husband to Debbie (Leslie Mann) and pursuing a career as a small-town cop. A car accident forces Steven to re-assess his life, and he elects to make changes. He admits to being gay, leaves Debbie and moves in with his new boyfriend, Jimmy (Rodrigo Santoro), and starts spending huge amounts of money to fund the "gay lifestyle." Since Steven doesn't have the money, he chooses to obtain it in the most expedient form possible: by becoming a con man. Eventually, this lifestyle catches up to him and he ends up in jail. There, he meets Phillip Morris (Ewan McGregor), who becomes the love of his life. Once out of prison, however, Steven can't resist the allure of his old ways, but this time his schemes become more audacious... and lucrative.

Perhaps the most disappointing aspect of I Love You Phillip Morris is its inability to maintain the high level at which it begins - a withering lampoon of wholesome, middle class values. At some point, the movie decides it wants us to take its characters seriously and become invested in their relationship, and that's when I Love You Phillip Morris loses a share of its sense of fun. Even with Carrey's fine performance on display in nearly every scene, the movie can't help spinning its wheels. At times, there's a twisted resemblance to Steven Spielberg's Catch Me if You Can. Steven is as slippery as an eel, but every time he gives the authorities the slip, he never quite gets away. Some of the means by which he facilitates his escape are so complex that it's a shame they net him only a short span of liberty. It's as if Steven invests all his creative energy into planning the getaway, but doesn't think much about what happens after he succeeds.

On more than one occasion, Carrey's performance dwarfs the material benefitting from his work; it will be interesting to see if the buzz is sufficient to warrant an Oscar nomination. The romance is a persistent flaw - not because it shows two men in love but because their relationship feels artificial. We recognize that Steven and Phillip are in love because it's a plot point. We're told it. But we don't feel it, and that emotional component - or its absence - is what prevents I Love You Phillip Morris from becoming all it aspires to be. It's an entertaining diversion that contains unrealized elements of something better.